Since interior parts of vehicles such as automobiles, in particular an instrument panel, are located in front of a driver, it is not preferable that light in the visible region is reflected by the interior parts, thus dazzling the driver, because this may exert a harmful influence on driving. From such a standpoint, a dark color such as black is generally used for an instrument panel in an automobile. However, these dark color parts generally used also absorb light in the near-infrared region in addition to light in the visible region at the same time, so that temperature in an automobile rises due to the heating of the surfaces of these dark color parts. In addition, this temperature rise in an automobile leads to use of air conditioner, resulting in poor fuel efficiency. Such temperature rise in a vehicle caused by sunlight is a problem arising not only in an instrument panel but also in all dark color vehicle interior parts.
In ball stadiums such as baseball stadiums and soccer stadiums, a bench seat surface with a color reflecting light in the visible region is not preferable. In addition, with respect to membrane materials used for a tent, an awning, a truck tarp, and the like, the membrane materials which reflect light in the visible region are not preferable in some cases because such membrane materials are dazzling human eyes. Thus, dark color materials are used for these applications, but these materials have a problem of temperature rising of the surface thereof as described above.
Incidentally, a technique providing a film or a sheet having heat shielding properties has been used in the past, and, for example, Japanese Patent Application Publication No. Hei 8-81567 (Document 1) discloses a sheet having heat shielding properties by containing a specific amount of an aluminum compound or a diimonium compound in a plastic resin. In addition, Japanese Patent Application Publication No. Hei 10-250002 (Document 2) discloses a film for outdoor spreading use which has heat shielding properties enhanced by providing a layer containing fine particles of an inorganic oxide doped with a metal on one surface of a thermoplastic resin film and further providing a layer containing hydrophilic inorganic colloidal particles. Moreover, Japanese Patent Application Publication No. 2002-12679 (Document 3) discloses a heat shielding color film formed by mixing two or more pigments having heat shielding properties in a thermoplastic resin film.
Sheets and films described in Document 1 and 2 are translucent, and are preferably used for applications which need transparency, such as lamination to a glass window. However, these sheets and films are not preferable for a dark color sheet-like body as of the present invention. In addition, a sheet as described in Document 3 can be colored, but this sheet has solar radiation reflection property in not only the near-infrared region but also the visible region, so that it is difficult to have both heat shielding properties and a dark color.
In addition, Japanese Patent Translation Publication No. 2004-505808 (Document 4) discloses a structural body not absorbing heat at its surface with a structure for absorbing light in the visible region but reflecting light in the near-infrared region.
Moreover, Japanese Patent Application Publication No. 2004-314596 (Document 5) discloses a colored sheet having light ray shielding properties, comprising at least a reflection layer and a colored layer laminated on an light-exposed side of the reflection layer, wherein the reflection layer has a solar radiation reflection ratio of 60% or more in a wavelength region of 780 to 1350 nm, and the colored layer has a light transmission ratio of 30% or more in a wavelength region of 780 to 1350 nm as well as having a solar radiation absorption ratio of 10 to 80% in a wavelength region of 380 to 780 nm. However, since the colored layer of the sheet described in Document 5 has a wide solar radiation absorption ratio of 10 to 80% in a wavelength region of 380 to 780 nm, relatively flexible coloring was possible, but a sheet with a dark color could not be obtained.